1. Field of the Invention
This invention relates to electronic engine controls, particularly those having an air flow meter.
2. Prior Art
Electronic engine control using sensors and actuators coupled to a computer processing unit is known. For example, it is known to determine a voltage representative of air flow into the engine and apply it to a central electronic engine control module. A transfer function or stored table within the control module transforms the actual received voltage into an air flow measurement. Typically, a fuel calculation using the derived air flow is then performed to determine the amount of fuel to be supplied to the engine. However, it has been found that it is desirable to correct the value of the calculated fuel. That is, the air flow may not be sufficient to provide a sufficiently adequate determination of fuel. For example, a memory associated with the central computer processor may store a correction multiplier which can be applied to the fuel calculation to get a corrected fuel calculation. The correction multiplier may be stored as a function of engine load and/or engine RPM. The correction multiplier can be applied to the fuel calculation as a multiplier and a corrected fuel calculation derived.
The above methodology may be undesirable because the correction multiplier is stored as a function of load which is a calculated value. Such a calculation introduces inaccuracies and takes time. Accuracy may be lost because of rounding off during multiplication and because of the change in engine conditions due to the passage of time since the initial voltage was supplied to the electronic engine control module. Also, the table storing the correction multiplier is typically a three dimensional table which uses storage space, requires two inputs and has a calculated output.
It would be desirable to have increased accuracy, require less storage space, and a reduced cost of memory and processing equipment. These are some of the problems this invention overcomes.
Fuel injected systems may exhibit vehicle to vehicle steady state air fuel ratio errors due to normal variability in system components. Accordingly, an adaptive air flow strategy would be desirable to address this problem. For example, such a system can store the characteristics of the individual system components. This stored information can be used to predict what the system will do based on past experience. Such an ability to predict system behavior improves both open loop and closed loop fuel control. For example, the stored information can be used on cold starts to achieve better open loop fuel control before an exhaust gas oxygen sensor reaches operating temperature to supply information about the air fuel ratio of the engine during operation. Accordingly, a benefit of such an adaptive strategy is to reduce the effects of product variability.